The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
Lasers are used for the alignment of development headings in underground mines. In particular, pen-sized lasers are being used for the alignment of development relative short headings.
The use of pen-sized lasers has its difficulties. Typically, mounting of these types of lasers on the walls of the headings is a cumbersome procedure. This is because typically brackets and bolting are required for attaching the laser to the wall.
Anchoring means have been developed for fastening the lasers to the walls. However, these anchoring means include switch means that are, for example, turned on and off during attachment of the laser to the anchoring means. In particular, during attachment of the laser to the anchoring means, an electric circuit is closed turning on the laser; during detachment of the laser from the anchoring means, the electric circuit is broken turning off the laser.
These anchoring means have several drawbacks. In particular, the fact that the anchoring means include the switch means increases the production costs of the anchoring means. Also, these anchoring means include working parts that easily get damaged during fastening of the anchoring means to the walls of the mine headings and during operation of the lasers. This is particularly, true in view that the survey instruments are being operated in underground mines.
Further, the fact that the laser can only be turned on and off when being attached or detached to the anchoring means is particular disadvantageous. This is because the laser can only be used in conjunction with the attachment means.
It is against this background that the present invention has been developed.